A flyback AC/DC converter using power semiconductor filter for input power factor correction

An application of an input current harmonic filtering technology, namely power semiconductor filter (PSF), for conventional flyback AC/DC converter will be presented. By connecting a series-pass device (SPD) in series with the input of the flyback converter, the input current of the entire system has the waveform profiled to be in phase with the supply voltage and its magnitude adjusted to perform output regulation. To minimize the loss of the SPD, its operating point is kept at the boundary between the active and saturation region through controlling the duty cycle of the switch in the flyback converter. A 100W, 85-265Vac / 36Vdc flyback AC-DC converter prototype has been built. A comprehensive study into the performance characteristics, additional loss due to the SPD, and thermal distribution of the system will be given. Results reveal that the input power factor can be kept above 0.995 over the operating range.